In releases 8 to 11 of an LTE (Long Term Evolution) system, a PDCCH (physical downlink control channel) needs to be sent on at least one carrier, where the PDCCH is mainly used for scheduling uplink and downlink data transmission. A CRS (cell-specific reference signal) may be sent on the foregoing carrier, a CRS may be transmitted at least in a subframe within a time-frequency resource area of transmission control information, and a CRS may be transmitted in a time-frequency resource area of transmission control information on entire bandwidth. In addition, a CRS may be transmitted in a non-MBSFN (Multimedia Broadcast multicast service Single Frequency Network) subframe in a time-frequency resource area of transmission data information, and a CRS is also transmitted in a time-frequency resource area of transmission data information on entire bandwidth. The CRS may be used by a UE to demodulate a control channel and a data channel, so as to perform measurement of RRM (radio resource management) and CSI (channel state information), and perform time and frequency synchronization with a base station.
A CA (carrier aggregation) technology is introduced in LTE-A release 10. For a UE (user equipment) that supports a carrier aggregation capability, a base station may configure multiple carriers for the UE, and the multiple carriers may include one anchor carrier and multiple supplementary carriers, so that the UE simultaneously uses the multiple carriers to perform uplink and downlink communication, thereby supporting high-speed data transmission.
In LTE release 12 and a later release, a new carrier type is proposed, that is, an NCT (new carrier type). An NCT carrier may be a non-backward compatible carrier, and transmission of a cell-common reference signal, such as a CRS, in a subframe on the NCT carrier may be eliminated or reduced to improve carrier performance, for example, spectrum efficiency may be improved, heterogeneous network support may be improved, and energy saving is achieved. In a case in which transmission of a cell-common reference signal, such as a CRS, is reduced, transmission of some reserved cell-specific reference signals, such as CRSs, is mainly used by a UE to perform time and frequency tracking processing and referencing. This new carrier type may be used by, for example, a UE of the LTE release 12 and a UE of a release later than the LTE release 12.
Because the NCT carrier does not have backward compatibility, a UE of a release earlier than the LTE release 12 cannot use the NCT carrier. The UE of the release earlier than the LTE release 12 is referred to as a UE of an old release. The UE of an old release is a UE that cannot recognize an NCT carrier, and does not support performing communication by using an NCT carrier. To ensure that the UE of an old release communicates normally, for a cell in which the UE of an old release exists, an operator cannot deploy the NCT carrier, and cannot obtain a carrier performance gain caused by introduction of the NCT, which leads to relatively low carrier resource utilization in the cell.